In vivo degradation and bone response of a composite coating on Mg-Zn-Ca alloy prepared by microarc oxidation and electrochemical deposition.

Composite coatings with hydroxyapatite (HA), octacalcium phosphate (OCP) in electrochemical deposition (ED) layers and MgO, Mg3 (PO4 )2 in microarc oxidation (MAO) layers were prepared by ED and MAO on Mg-Zn-Ca alloy to improve the corrosion resistance and bone response. Substrates and coated samples were implanted in the femur shaft of rabbits to observe in vivo degradation behavior during 50 weeks. Results showed that the degradation rate of the substrates was much faster than the coated at 8, 12 weeks and became close to the coated at 18 weeks postoperatively. The composite coatings prevented the substrate from rapid release of magnesium ions at the interface and gradually degraded at the same time. The composite coatings induced more newly formed bone tissue and faster bone response. Overall, reduced degradation rate and improved bone response were achieved by the composite coatings. Thus, the composite coatings on Mg-Zn-Ca alloy are promising for clinical application in the future.